overflow.h: Add flex_array_size() helper (b19d57d0) · Commits · 戴 / test

Add flex_array_size() helper for the calculation of the size, in bytes, of a flexible array member contained within an enclosing structure. Example of usage: struct something { size_t count; struct foo items[]; }; struct something *instance; instance = kmalloc(struct_size(instance, items, count), GFP_KERNEL); instance->count = count; memcpy(instance->items, src, flex_array_size(instance, items, instance->count)); The helper returns SIZE_MAX on overflow instead of wrapping around. Additionally replaces parameter "n" with "count" in struct_size() helper for greater clarity and unification. Signed-off-by:

Gustavo A. R. Silva <gustavoars@kernel.org> Link: https://lore.kernel.org/r/20200609012233.GA3371@embeddedor Signed-off-by:

Kees Cook <keescook@chromium.org>

include/linux/overflow.h

+21 −4

Original line number	Diff line number	Diff line
		@@ -304,16 +304,33 @@ static inline __must_check size_t __ab_c_size(size_t a, size_t b, size_t c)
		* struct_size() - Calculate size of structure with trailing array.
		* @p: Pointer to the structure.
		* @member: Name of the array member.
		* @n: Number of elements in the array.
		* @count: Number of elements in the array.
		*
		* Calculates size of memory needed for structure @p followed by an
		* array of @n @member elements.
		* array of @count number of @member elements.
		*
		* Return: number of bytes needed or SIZE_MAX on overflow.
		*/
		#define struct_size(p, member, n) \
		__ab_c_size(n, \
		#define struct_size(p, member, count) \
		__ab_c_size(count, \
		sizeof(*(p)->member) + __must_be_array((p)->member),\
		sizeof(*(p)))

		/**
		* flex_array_size() - Calculate size of a flexible array member
		* within an enclosing structure.
		*
		* @p: Pointer to the structure.
		* @member: Name of the flexible array member.
		* @count: Number of elements in the array.
		*
		* Calculates size of a flexible array of @count number of @member
		* elements, at the end of structure @p.
		*
		* Return: number of bytes needed or SIZE_MAX on overflow.
		*/
		#define flex_array_size(p, member, count) \
		array_size(count, \
		sizeof(*(p)->member) + __must_be_array((p)->member))

		#endif /* __LINUX_OVERFLOW_H */

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